1. Field of The Invention
The present invention relates to improvements in the manufacturing of reclosable plastic bags, and, more particularly, to a method which permits such bags to be formed as they are fed over a filling spout of a filling machine whereby the bags are formed and simultaneously filled with a product.
2. Description of the Prior Art
The art of making reclosable plastic bags provided with mating profiles which form a zipper to render the bags reclosable is well-defined in prior patents. Examples of such patents are U.S. Pat. Nos. 4,709,533; 4,894,975; and 5,046,300.
U.S. Pat. No. 4,709,533 shows an apparatus and a method wherein film is fed downwardly wrapped around a form-fill tube and the edges of the film are brought together pressed between pressing rollers guiding the edges together so that an outer seal can be formed. Means are provided for feeding interlocked zipper members between the film layers and between the rollers and the filling spout. Following the rollers, there are located uniquely positioned and shaped bars which include inner bars that have a space between them to guide the center portion of the zipper and these bars also form a backing for outer heated bars which seal the webs of the zipper to the inner surface of the bag film. The outer bars also extend around the edges of the bag to simultaneously form an outer security seal or lip seal. The thus formed and sealed zipper tube is filled through the spout and cross-seals with cross-cutters to complete the individual bags.
U.S. Pat. No. 4,894,975 also shows an apparatus and method wherein film is fed downwardly wrapped around a form-fill tube and the edges of the film are brought together in adjacency. The adjacent edges of the film are joined such as by heat sealing to interlocked zipper members, which thereafter form the sole juncture between the edges of the film and which zipper members provide a reclosable opening for the top of the completed bag. A web extends between the zipper strips, either above or below the interlocking elements, which web can be constructed of a weight and width with optimum characteristics for forming a security seal at the top of the bag and forming a tamper-evident seal. In a single rapid operation, a bag is formed wherein the film of the bag has optimum characteristics for the bag, and the plastic of the zipper and of the web therebetween have optimum characteristics for the functions of the zipper and functions of the security tamper-evident seal. The thus formed and sealed zipper tube is filled through the spout and cross-sealed with cross-cutters to complete the individual bags.
U.S. Pat. No. 5,046,300 shows a method and apparatus for forming reclosable packages wherein a flat packaging film is formed over a forming shoulder and into a tubular shape about a central member. The packaging film is advanced vertically downward along the length of the central member, and a reclosable profile element is threaded inside the tubular shape of the packaging film. The tubular packaging film is deformed to form a longitudinally extending loop of packaging film, and the interlocked zipper members are guided into the loop. The interlocked zipper members are then adhered to the inner surface of the loop of packaging film. The thus formed and sealed zipper tube is filled through the spout and cross-sealed with cross-cutters to complete the individual bags. It should be noted, that in each of the above described prior art methods some portion of the film is drawn away from the fill tube at substantially a right angle to the fill tube to receive and be sealed to the zipper strips. This additional film causes a problem of potential wrinkling of the film at the cross seal locations.
U.S. patent application Ser. No. 08/226,288, filed on Apr. 11, 1994 and commonly assigned, shows a method for forming reclosable packages on a conventional form-fill-and-seal (FFS) machine, wherein a "Y-type" zipper strip having closed profiles is fed toward and longitudinally down the filling spout thereof. A thermoplastic film is wrapped around the filling spout enclosing the zipper strip, and the lateral edges of the film are bonded together to form a longitudinal seam. The zipper strip webs are attached by sealing bars to the inside of the tube so formed from the thermoplastic film between the fill tube and the sealing bars. At intervals, transverse seams are formed to produce individual reclosable packages, which may also be separated from one another. The packages are filled with product during the course of their manufacture. In all of the above mentioned inventions the zipper strip is always delivered to the fill tube in interlocked condition.
The present invention represents an alternate approach toward the attachment of reclosable profile elements to a tubular packaging film, and toward the formation of reclosable plastic bags containing a product, wherein the profile elements are enclosed within a tube of thermoplastic film and attached to the inner surface thereof on the fill tube of a form-fill-and-seal machine in an uninterlocked condition. This method provides a number of advantages. It minimizes the likelihood of the formation of wrinkles in the film in the cross seal area and allows different zipper constructions to be relatively easily interchanged in the form-fill-and-seal machine.